The long range objective of these studies is to evaluate the role(s) of cyclic nucleotides in blood vessels, especially regarding the response of vascular smooth muscle to catecholamines and other vasoactive agents. The specific aims are: 1) The determination of cycic AMP and cyclic GMP in vascular tissue in response to agents that induce contraction or relaxation. 2) The characterization of cyclic nucleotide phosphodiesterase in vascular tissue. 3) The characterization of adenylate and guanylate cyclase activites in vascular tissue. 4) The evaluation of effects of exogenous cyclic nucleotides and derivatives on vascular contraction. Bibliographic references: Cyclic Nucleotide Phosphodiesterase Activities of Pig Coronary Arteries. J.N. Wells, C.E. Baird, Y.J. Wu and J.G. Hardman, Biochim. Biophys. Acta, 384: 430, 1975; Effects of Norepinephrine on Cyclic Nucleotide Levels in the Ductus Deferens of the Rat. Schultz, K. and Hardman, J.G. Metabolism 24:429, 1975.